Discharge cone

ABSTRACT

A device for discharging a fine-grained solid from a container wherein the container has a discharge cone in the lower area, which opens into a discharge opening and discharge device, a mechanism for fluidizing or loosening the solid are provided the discharge cone has at least one offset in the form of a gap the offset having openings a gas can be fed through each of the openings of the gap-shaped offsets, each of the gap-shaped offsets is covered toward the center axis of the discharge cone, the gap-shaped offsets are not directed toward the center axis of the discharge cone, and wherein the gaps of the gap-shaped offsets are closed by cover pates which have round or slit-shaped openings, and the gaps extend in the downward direction.

Thermal conversion of solid fuels, e.g. most different types of coal, peat, hydrogenation residues, residual materials, waste, biomasses, and fly dust or a mixture of these substances is often performed under elevated pressure and at high temperature with the aim to generate a crude synthesis gas with a high content of energy and/or with a composition that is favorable for further chemical syntheses. Feasible thermal conversion processes may for example be pressurized combustion or pressurized gasification according to the fluidized bed or flue stream process.

These processes require comminution of fuels stored at normal pressure and ambient conditions to obtain fine particles and bringing these particles to the pressure level of a thermal conversion in order to enable their conveyance into the pressurized reactor. A conveyance and intermediate storage of finely pulverized fuels is necessary for this purpose. To bring the fuel to the pressure level of the reactor, sluice systems in which the fuel is elevated to the required pressure in tanks arranged one behind the other are commonly used. The crucial criterion for operational safety is the reliable ability to empty the tanks, even after these tanks have been elevated to high system pressures.

To safely discharge extremely fine and fine-grained solids from a tank, various approaches are in principle feasible according to the commonly known prior art of technology:

-   -   In large silos exposed to atmospheric pressure, solid material         is often withdrawn by means of mechanical devices, e.g. reamer         arms etc.     -   In principle, a solid matter bulk charge can be converted into a         fluidized bed state by supplying gas contrary to gravity force.         In this case, the fluidized bed behaves similarly to a liquid         and can flow out through exit ports, lateral nozzles, etc. A         drawback lies in that large amounts of gas are needed. This         situation is further aggravated by the fact that very fine         particles can only be converted with extreme difficulty into a         homogeneous fluidized bed.     -   Another possibility to allow for a solid matter discharge from a         tank lies in providing conical outlet geometries, considering         the properties of the bulk material. The solid matter outflow         from a cone can be supported by adding gas via or at the cone         walls. The gas quantity is usually smaller than the quantity         that would be needed for fluidization, but it is sufficient to         render the wall friction of the bulk material ineffective and/or         to prevent local trends for bridging.

The latter method is the preferred variant in gasification plants described hereinabove where fine-grained fuels must be handled both at atmospheric and high pressures. To this effect, the required gas quantity is limited while mechanical internals are dispensed with at the same time.

Feeding gas via porous elements into the discharge cone represents the state of prior art in technology. Porous elements preferably are comprised of sinter metal, but they may also be comprised of other porous media. The use of porous materials entails some disadvantages in terms of process and operational technology:

-   -   The admissible pore size orientates itself by the solid matter         to be handled and/or by its particle grain size range.         Accordingly, the pore size can only be reduced to a reasonable         measure which results from the desired retained particle size         and from the throughflow pressure loss. In practice it becomes         evident that the porous medium gets clogged as time goes by,         even with very small pore sizes. The reason is that the finely         pulverized fuel to be handled always has a particle grain size         range within which even finest particles occur that may deposit         in the pores. Moreover, abrasive effects of the fuel within a         tank and on handling the fuel entail the development of finest         particles which would also clog the pores. Though it is tried to         counteract a clogging of the porous medium by permanently         feeding-in a stream of gas, implementation in practice shows         that this is only suitable to prolong the service life of porous         elements while the basic problem persists.     -   Porous material inevitably has less strength than a comparable         solid material, and therefore, if accompanied by gas charging,         it may only be operated in a manner that a maximally admissible         pressure loss over the porous material, i.e. a mechanically         impacting force resulting from the pressure difference and the         covered area is not exceeded. Improper handling or non-secured         pressure rises in operation may therefore lead to a destruction         of the porous material.     -   Another process technology related drawback lies in that porous         materials may only be charged with particle-free gas. For         example, it is impossible to use gas contaminated with gas and         coming from tank expansions, because porous materials would get         clogged from the gas feeding side.     -   Processing of porous material in conjunction with steels         utilized in classical vessel manufacture calls for special         manufacturing capabilities, skills and experience, particularly         in case of a high-grade welding of sinter metals, for example.         This is highly costly and expensive.

The German patent specification DE 41 08 048 C2 discloses gas feeder elements that are introduced into the cone-shaped part of a pressure pot in order to achieve a fluidization of the solid material bulk charge with the aim to bring about a pneumatic conveyance from out of the pressure pot. To this effect, tube elements equipped with bores to allow for gas feeding are mounted on the interior sides of the cone.

EP 348 008 B1 proposes to ensure a constant solid matter mass flow from a tank with a conical outlet by feeding gas through a central pipe inserted vertically from the top into the solid matter bulk charge near the outlet and in the conical tank section. In addition, gas is supplied via the conical walls, said conical walls being designed and constructed as a porous medium.

WO 2004/085578 A1 discloses a sluice container providing gas feeder elements inside in the conical container section through which the container is brought to the target pressure. The elements are provided with porous element through which the gas is supplied.

Proposed in U.S. Pat. No. 5,106,240 A is a cone which provides for a plurality of porous elements through which gas is fed into the solid material bulk charge with the aim to obtain an equalized and uniform solid matter flow.

WO 89/11378 A1 proposes to feed gas by inserting porous elements in the cone of a silo in order to allow for an even and uniform flow of material. The same aim is pursued by the gas feeding device disclosed in U.S. Pat. No. 4,941,779 A. The difference lies in that the device described immerses into the bulk charge, supplies gas there partially in order to also ensure the most uniform possible flow of material from a drain port provided there. Here, too, porous elements are employed in order to feed gas into the bulk charge composed of fine particles.

US 2006/013660 A1 in detail describes a fluidizing cone including the required connecting flanges which is fastened to a tank. According to this description, the conical interior walls are made of a porous material.

CH 209 788 describes a reservoir tank for dust-like goods with a hopper terminating into a downcomer in which a thin layer of air migrates at the hopper wall towards the downcomer without approaching the center of the hopper, while air ascending through the center of the hopper forces the dust outwardly against the hopper wall, thus preventing a formation of bridges.

Now, therefore, it is the object of the present invention to provide a discharge cone charged with gas for the discharge of a fine-grain solid matter from a tank that overcomes process technology related drawbacks entailed on the use of porous materials, and which fulfils the following requirements:

-   -   No use of porous materials,     -   Independence from the particle grain size range of the bulk         material,     -   Applicability of gases burdened with particles for gas feeding,     -   No limitation in the admissible pressure loss.

The inventive discharge cone solves this task in that

-   -   the tank has a discharge cone in its lower area,     -   which terminates into a discharge port and discharge device,     -   means for fluidizing or aeration of the solid matter are         provided for,     -   the discharge cone has at least one projection in form of a gap         and having apertures,     -   a gas can be supplied through each of these apertures of the         slotted projections,     -   characterized in that     -   each of the slotted projections is concealed towards the central         axis of the discharge cone,     -   the slotted projections are not aligned to the central axis of         the discharge cone, and wherein     -   the slots of the slotted projections are closed by cover metal         sheets which have round or slit-shaped apertures,     -   the slots extend in downward direction.

In one configuration it is envisaged that the slots are formed by laterally overlapping cone sectors. In further configurations it is envisaged that the slots extend in oblique direction and that the gas exit side is spirally aligned both in tangential and in the direction of the exit aperture, i.e. that it also has a radial-vertical portion. Accordingly, it may also be envisaged that the slots are formed by sections overlapping one above each other in form of oblique cone sections.

Further configurations relate to the slots and their apertures through which gas is fed in. Thus, for example, the slots can be closed by cover metal sheets which have round or slit-shaped apertures. The apertures may also have the shape of a nozzle jet. The apertures are preferentially larger than the largest particle diameter of the solid matter in the discharge cone. The thickness of the cover metal sheets can be so chosen that it is 3 times larger than the bore diameter in order to give the gas beam a specific direction. In the upper area of the slots, the apertures can be provided at smaller distances than in the lower area of the slots. Likewise, the holes may have larger cross-sections in the upper area than in the lower area so as to be able to supply a gas stream which is related to the cone cross-sectional area and adapted to the relevant level.

Instead of holes, exit tubes or exit nozzle jets may also be employed in other advantageous configurations, with it being possible to choose the spatial angles in which the gas beam enters into the discharge cone. Ideal—depending on the discharge material—are angles towards the horizontal plane of 30 degrees directed upwardly or downwardly, and angles of up to 45 degrees in the horizontal plane, measured from the circle tangent adjacent to the gas exit point, towards the center axis of the discharge cone.

The inventive device is explained in more detail by way of 5 drawings, these drawings only representing practical examples for the construction of the inventive device.

FIG. 1 shows a storage tank 1 with an inventive discharge cone 5.

FIGS. 2 and 3 illustrate a discharge cone with slots extending in vertical direction.

FIG. 4 shows a variant with modified inlet apertures.

FIG. 5 illustrates a discharge cone with slots which have an oblique angle towards the center axis.

FIG. 1 shows a storage tank 1 with an inventive discharge cone 5, into which the finely pulverized fuel 2 is transported pneumatically or gravimerically. The gas 3 exits from the storage tank 1 via gas filter 4, whereas the finely pulverized fuel gets into the storage tank 1 where it sinks down into the discharge cone 5. In the case of a pneumatic filling of the storage tank 1, the gas 3 is comprised of the transport gas and of the gas which is displaced in the tank by the solid matter brought in. In the case of a gravimetrical filling, the gas 3 is mainly comprised of displaced gas. The discharge cone 5 encompasses a pressure jacket 6 which is charged with pressurized gas 7. The withdrawal 9 of the finely pulverized fuel is realized through the sluice 8.

FIGS. 2 and 2 each show one discharge cone 5 with slots 10 which extend in vertical direction and from which the gas 3 streams out in tangential direction. FIG. 2 also shows half the opening angle γ of the discharge cone. The slots are closed with metal sheets 11 into which bores 12 are inserted through which pressurized gas 7 from the pressurized jacket 6 can be introduced into the discharge cone 5. While FIG. 3 shows slots 10 which viewed from the center line are concealed and have a projection 13, the slots 10 shown in FIG. 2 are open. The variant illustrated in FIG. 3 bears an advantage in that no angle of repose can build-up in front of the bores 12 and in that a reflux of finely pulverized fuel 2 through the bores 12 back into the pressurized jacket 6 is prevented even if there is no gas pressure applied there at a given moment, for example in intermittent mode of operation. However, the variant illustrated in FIG. 3 is more expensive to build.

FIG. 4 shows the variant illustrated in FIG. 3, but with modified inlet apertures to reduce the high strains and stresses which the cone wall is exposed to due to the tangential outflow of the gas stream from the aperture in slot 10. The inlet apertures are so modified that the beam direction of the escaping gas jet can be spatially aligned. Constructively this can be achieved by executing the metal sheets 11 (not drawn in FIG. 4) in the slots 10 as very massive metal sheets and by providing for accordingly fine bores 12 which are inserted in defined angles into the metal sheets 11, or by providing thin metal sheets 11 at which thin exit tubes or exit nozzle jets 14 are mounted which for example can be aligned by simple bending into the appropriate direction. Such exit tubes or exit nozzle jets 14 are preferentially mounted flush on the conus inside, protruding on the side facing the exterior space so that the direction of beam can be aligned with simple means on the protruding side.

With advantage the following angles are set for the alignment of the exit tubes or exit nozzle jets 14. Accordingly, a Cartesian coordinate system is taken as the basis. Its point of origin lies in the piercing point, one vertical y-z plane of which extends in parallel to the cone center axis and the other vertical x-y plane of which intersects the cone center axis, and the third x-z plane of which represents the horizontal plane. Contemplated in FIG. 4 are the angles of the axis of the exit tubes and/or exit nozzle jets 14 on the outside of the discharge cone where they are easy to measure in mounted state. The same applies analogously to the corresponding gas exit angles into the discharge cone.

Accordingly, the angle a lies between the projection 15 of the beam axis, which corresponds to the axis of the exit tubes or exit nozzle jets 14, on the horizontal x-z-plane, and the tangent 16, which rests on a horizontal section of the cone and extends through the point of origin of the coordinate system, between 0 and 45 degrees. Furthermore, the angle β lies between the beam axis which corresponds to the axis of the exit tubes or exit nozzle jets 14, and the horizontal x-z plane in a range of 30 degrees upwards to 30 degrees downwards.

FIG. 5 shows another discharge cone with downwardly directed slots 10 which extend in spiral direction. The slots 10 are also closed with metal sheets 11 into which bores 12 are inserted through which pressurized gas 7 from the pressurized jacket 6 can be introduced into the discharge cone 5. Owing to the spirally shaped arrangement, an outflow behaviour of the finely pulverized fuel similar to the one of a liquid outlet can be achieved.

LIST OF REFERENCE NUMBERS

-   1 Storage tank -   2 Finely pulverized fuel -   3 Gas -   4 Gas filter -   5 Discharge cone -   5 a Center line of the discharge cone -   6 Pressurized jacket -   7 Pressurized gas -   8 Sluice -   9 Withdrawal -   10 Slots -   11 Metal sheets -   12 Bores -   13 Ledge -   14 Exit tubes or exit nozzle jets -   14 a Center line of exit tubes or exit nozzle jets -   15 Projection -   16 Tangent 

1. A device for discharge of a fine-grain solid matter from a tank, wherein the tank has a discharge cone in its lower area, which terminates into a discharge port and discharge device, means for fluidizing or aeration of the solid matter are provided for, the discharge cone has at least one projection in form of a slot and having apertures, a gas can be supplied through each of these apertures of the slotted projections, wherein each of the slotted projections is concealed towards the central axis of the discharge cone, the slotted projections are not aligned to the central axis of the discharge cone, and wherein the slots of the slotted projections are closed by cover metal sheets which have round or slit-shaped apertures, the slots extend in downward direction.
 2. The device according to claim 1, wherein the slots are formed by laterally overlapping cone sectors.
 3. The device according to claim 1, wherein the slots extend in oblique direction and that the gas outlet side is spirally aligned both in tangential direction and in the direction of the outlet aperture.
 4. The device according to claim 3, wherein the slots are formed by sections overlapping one above the other in the form of oblique cone sections.
 5. The device according to claim 1, wherein the apertures are shaped in the form of nozzle jets.
 6. The device according to claim 1, wherein the diameters of the apertures are larger than the largest particle diameter of the fine-grained solid matter that is to be discharged from the tank.
 7. The device according to claim 1, wherein the thickness of the cover metal sheets is chosen to be at least three times greater than the bore diameter.
 8. The device according to claim 1, wherein the apertures in the upper area of the slots are provided for at smaller distances or have larger cross-sections, too, than in the lower area.
 9. The device according to claim 1, wherein the center lines of the apertures versus a tangent laid at the discharge cone form an angle of between 0 degrees and 45 degrees in the horizontal projection.
 10. The device according to claim 1, wherein the center lines of the apertures are inclined versus the horizontal plane at an angle of between 0 and 30 degrees upwards or downwards. 